Assessment of point-of-care measurement of urinary creatinine and electrolytes in the intensive care unit.

Abstract

Point of care technology makes it possible to measure blood and urine creatinine and electrolytes within the intensive care unit. We tested whether such point of care technology can accurately measure urine creatinine and electrolytes. We obtained urine from 28 patients for a total of 77 paired samples and measured creatinine and electrolytes using central laboratory technology and point of care technology. The mean difference in urine creatinine was 74 mcmol/L with 95% limits of agreement of -673 to 821 mcmol/L. The mean difference in urinary sodium was 0.282 mmol/L with 95% limits of agreement of -14 to 15 mmol/L. Significantly greater biases and wider limits of agreement were seen for potassium and chloride. We conclude that, despite the limited bias, due to wide limits of agreement, urinary creatinine and sodium cannot be estimated with point of care technology. Even greater inaccuracies make the estimation of potassium and chloride in urine by point of care technology not usable for clinical purposes.